Cross-talk generation in a multi-lane link during lane testing

ABSTRACT

A port of a computing device includes multiple receiver-transmitter pairs, each of the receiver-transmitter pairs including a respective receiver and a respective transmitter. The device further includes state machine logic that detects a training sequence received by a particular one of the receiver-transmitter pairs on a particular lane from a tester device. The training sequence includes a value to indicate a test of the particular receiver-transmitter pair by the tester device. The particular receiver-transmitter pair enters a first link state in association with the test and one or more other receiver-transmitter pairs of the port enter a second link state different from the first link state in association with the test to cause crosstalk to be generated on the particular lane during the test.

RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalPatent Application Ser. No. 62/614,874, filed Jan. 8, 2018, thedisclosure of which is incorporated by reference herein in its entirety.

FIELD

This disclosure pertains to computing system, and in particular (but notexclusively) to testing systems for point-to-point interconnects.

BACKGROUND

Advances in semi-conductor processing and logic design have permitted anincrease in the amount of logic that may be present on integratedcircuit devices. As a corollary, computer system configurations haveevolved from a single or multiple integrated circuits in a system tomultiple cores, multiple hardware threads, and multiple logicalprocessors present on individual integrated circuits, as well as otherinterfaces integrated within such processors. A processor or integratedcircuit typically comprises a single physical processor die, where theprocessor die may include any number of cores, hardware threads, logicalprocessors, interfaces, memory, controller hubs, etc.

As a result of the greater ability to fit more processing power insmaller packages, smaller computing devices have increased inpopularity. Smartphones, tablets, ultrathin notebooks, and other userequipment have grown exponentially. However, these smaller devices arereliant on servers both for data storage and complex processing thatexceeds the form factor. Consequently, the demand in thehigh-performance computing market (i.e. server space) has alsoincreased. For instance, in modern servers, there is typically not onlya single processor with multiple cores, but also multiple physicalprocessors (also referred to as multiple sockets) to increase thecomputing power. Servers may also be implemented using distributedcomputing, in rack scale architectures, and other alternativeimplementations. As the processing power grows along with the number ofdevices in a computing system, the communication between sockets andother devices becomes more critical.

In fact, interconnects have grown from more traditional multi-drop busesthat primarily handled electrical communications to full blowninterconnect architectures that facilitate fast communication.Unfortunately, as the demand for future processors to consume at evenhigher-rates corresponding demand is placed on the capabilities ofexisting interconnect architectures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a computing system including aninterconnect architecture.

FIG. 2 illustrates an embodiment of a interconnect architectureincluding a layered stack.

FIG. 3 illustrates an embodiment of a request or packet to be generatedor received within an interconnect architecture.

FIG. 4 illustrates an embodiment of a transmitter and receiver pair foran interconnect architecture.

FIG. 5 is a diagram illustrating an example link training state machine.

FIGS. 6A-6B are diagrams illustrating an example device connected to atester device to conduct testing of a particular lane of a link.

FIG. 7 is a diagram illustrating a portion of an example link trainingstate machine including specialized testing link states.

FIG. 8 is a block diagram illustrating an example device connected to atester device using an example compliance fixture device.

FIGS. 9A-9E are block diagrams illustrating signaling within exampletesting link states.

FIG. 10 illustrates an embodiment of a block diagram for a computingsystem including a multicore processor.

FIG. 11 illustrates an embodiment of a block for a computing systemincluding multiple processors.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth,such as examples of specific types of processors and systemconfigurations, specific hardware structures, specific architectural andmicro architectural details, specific register configurations, specificinstruction types, specific system components, specificmeasurements/heights, specific processor pipeline stages and operationetc. in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one skilled in the art thatthese specific details need not be employed to practice the presentinvention. In other instances, well known components or methods, such asspecific and alternative processor architectures, specific logiccircuits/code for described algorithms, specific firmware code, specificinterconnect operation, specific logic configurations, specificmanufacturing techniques and materials, specific compilerimplementations, specific expression of algorithms in code, specificpower down and gating techniques/logic and other specific operationaldetails of computer system haven't been described in detail in order toavoid unnecessarily obscuring the present invention.

Although the following embodiments may be described with reference toenergy conservation and energy efficiency in specific integratedcircuits, such as in computing platforms or microprocessors, otherembodiments are applicable to other types of integrated circuits andlogic devices. Similar techniques and teachings of embodiments describedherein may be applied to other types of circuits or semiconductordevices that may also benefit from better energy efficiency and energyconservation. For example, the disclosed embodiments are not limited todesktop computer systems or Ultrabooks™. And may be also used in otherdevices, such as handheld devices, tablets, other thin notebooks,systems on a chip (SOC) devices, and embedded applications. Someexamples of handheld devices include cellular phones, Internet protocoldevices, digital cameras, personal digital assistants (PDAs), andhandheld PCs. Embedded applications typically include a microcontroller,a digital signal processor (DSP), a system on a chip, network computers(NetPC), set-top boxes, network hubs, wide area network (WAN) switches,or any other system that can perform the functions and operations taughtbelow. Moreover, the apparatus', methods, and systems described hereinare not limited to physical computing devices, but may also relate tosoftware optimizations for energy conservation and efficiency. As willbecome readily apparent in the description below, the embodiments ofmethods, apparatus', and systems described herein (whether in referenceto hardware, firmware, software, or a combination thereof) are vital toa ‘green technology’ future balanced with performance considerations.

As computing systems are advancing, the components therein are becomingmore complex. As a result, the interconnect architecture to couple andcommunicate between the components is also increasing in complexity toensure bandwidth requirements are met for optimal component operation.Furthermore, different market segments demand different aspects ofinterconnect architectures to suit the market's needs. For example,servers require higher performance, while the mobile ecosystem issometimes able to sacrifice overall performance for power savings. Yet,it's a singular purpose of most fabrics to provide highest possibleperformance with maximum power saving. Below, a number of interconnectsare discussed, which would potentially benefit from aspects of theinvention described herein.

One interconnect fabric architecture includes the Peripheral ComponentInterconnect (PCI) Express (PCIe) architecture. A primary goal of PCIeis to enable components and devices from different vendors tointer-operate in an open architecture, spanning multiple marketsegments; Clients (Desktops and Mobile), Servers (Standard, Rack Scale,Cloud, Fog, Enterprise, etc.), and Embedded and Communication devices.PCI Express is a high performance, general purpose I/O interconnectdefined for a wide variety of future computing and communicationplatforms. Some PCI attributes, such as its usage model, load-storearchitecture, and software interfaces, have been maintained through itsrevisions, whereas previous parallel bus implementations have beenreplaced by a highly scalable, fully serial interface. The more recentversions of PCI Express take advantage of advances in point-to-pointinterconnects, Switch-based technology, and packetized protocol todeliver new levels of performance and features. Power Management,Quality Of Service (QoS), Hot-Plug/Hot-Swap support, Data Integrity, andError Handling are among some of the advanced features supported by PCIExpress.

Referring to FIG. 1, an embodiment of a fabric composed ofpoint-to-point Links that interconnect a set of components isillustrated. System 100 includes processor 105 and system memory 110coupled to controller hub 115. Processor 105 includes any processingelement, such as a microprocessor, a host processor, an embeddedprocessor, a co-processor, or other processor. Processor 105 is coupledto controller hub 115 through front-side bus (FSB) 106. In oneembodiment, FSB 106 is a serial point-to-point interconnect as describedbelow. In another embodiment, link 106 includes a serial, differentialinterconnect architecture that is compliant with different interconnectstandard. In some implementations, the system may include logic toimplement multiple protocol stacks and further logic to negotiationalternate protocols to be run on top of a common physical layer, amongother example features.

System memory 110 includes any memory device, such as random accessmemory (RAM), non-volatile (NV) memory, or other memory accessible bydevices in system 100. System memory 110 is coupled to controller hub115 through memory interface 116. Examples of a memory interface includea double-data rate (DDR) memory interface, a dual-channel DDR memoryinterface, and a dynamic RAM (DRAM) memory interface.

In one embodiment, controller hub 115 is a root hub, root complex, orroot controller in a Peripheral Component Interconnect Express (PCIe orPCIE) interconnection hierarchy. Examples of controller hub 115 includea chipset, a memory controller hub (MCH), a northbridge, an interconnectcontroller hub (ICH) a southbridge, and a root controller/hub. Often theterm chipset refers to two physically separate controller hubs, i.e. amemory controller hub (MCH) coupled to an interconnect controller hub(ICH). Note that current systems often include the MCH integrated withprocessor 105, while controller 115 is to communicate with I/O devices,in a similar manner as described below. In some embodiments,peer-to-peer routing is optionally supported through root complex 115.

Here, controller hub 115 is coupled to switch/bridge 120 through seriallink 119. Input/output modules 117 and 121, which may also be referredto as interfaces/ports 117 and 121, include/implement a layered protocolstack to provide communication between controller hub 115 and switch120. In one embodiment, multiple devices are capable of being coupled toswitch 120.

Switch/bridge 120 routes packets/messages from device 125 upstream, i.e.up a hierarchy towards a root complex, to controller hub 115 anddownstream, i.e. down a hierarchy away from a root controller, fromprocessor 105 or system memory 110 to device 125. Switch 120, in oneembodiment, is referred to as a logical assembly of multiple virtualPCI-to-PCI bridge devices. Device 125 includes any internal or externaldevice or component to be coupled to an electronic system, such as anI/O device, a Network Interface Controller (NIC), an add-in card, anaudio processor, a network processor, a hard-drive, a storage device, aCD/DVD ROM, a monitor, a printer, a mouse, a keyboard, a router, aportable storage device, a Firewire device, a Universal Serial Bus (USB)device, a scanner, and other input/output devices. Often in the PCIevernacular, such as device, is referred to as an endpoint. Although notspecifically shown, device 125 may include a PCIe to PCI/PCI-X bridge tosupport legacy or other version PCI devices. Endpoint devices in PCIeare often classified as legacy, PCIe, or root complex integratedendpoints.

Graphics accelerator 130 is also coupled to controller hub 115 throughserial link 132. In one embodiment, graphics accelerator 130 is coupledto an MCH, which is coupled to an ICH. Switch 120, and accordingly I/Odevice 125, is then coupled to the ICH. I/O modules 131 and 118 are alsoto implement a layered protocol stack to communicate between graphicsaccelerator 130 and controller hub 115. Similar to the MCH discussionabove, a graphics controller or the graphics accelerator 130 itself maybe integrated in processor 105. Further, one or more links (e.g., 123)of the system can include one or more extension devices (e.g., 150),such as retimers, repeaters, etc.

Turning to FIG. 2 an embodiment of a layered protocol stack isillustrated. Layered protocol stack 200 includes any form of a layeredcommunication stack, such as a Quick Path Interconnect (QPI) stack, aPCIe stack, a next generation high performance computing interconnectstack, or other layered stack. Although the discussion immediately belowin reference to FIGS. 1-4 are in relation to a PCIe stack, the sameconcepts may be applied to other interconnect stacks. In one embodiment,protocol stack 200 is a PCIe protocol stack including transaction layer205, link layer 210, and physical layer 220. An interface, such asinterfaces 117, 118, 121, 122, 126, and 131 in FIG. 1, may berepresented as communication protocol stack 200. Representation as acommunication protocol stack may also be referred to as a module orinterface implementing/including a protocol stack.

PCI Express uses packets to communicate information between components.Packets are formed in the Transaction Layer 205 and Data Link Layer 210to carry the information from the transmitting component to thereceiving component. As the transmitted packets flow through the otherlayers, they are extended with additional information necessary tohandle packets at those layers. At the receiving side the reverseprocess occurs and packets get transformed from their Physical Layer 220representation to the Data Link Layer 210 representation and finally(for Transaction Layer Packets) to the form that can be processed by theTransaction Layer 205 of the receiving device.

Transaction Layer

In one embodiment, transaction layer 205 is to provide an interfacebetween a device's processing core and the interconnect architecture,such as data link layer 210 and physical layer 220. In this regard, aprimary responsibility of the transaction layer 205 is the assembly anddisassembly of packets (i.e., transaction layer packets, or TLPs). Thetranslation layer 205 typically manages credit-base flow control forTLPs. PCIe implements split transactions, i.e. transactions with requestand response separated by time, allowing a link to carry other trafficwhile the target device gathers data for the response.

In addition PCIe utilizes credit-based flow control. In this scheme, adevice advertises an initial amount of credit for each of the receivebuffers in Transaction Layer 205. An external device at the opposite endof the link, such as controller hub 115 in FIG. 1, counts the number ofcredits consumed by each TLP. A transaction may be transmitted if thetransaction does not exceed a credit limit. Upon receiving a response anamount of credit is restored. An advantage of a credit scheme is thatthe latency of credit return does not affect performance, provided thatthe credit limit is not encountered.

In one embodiment, four transaction address spaces include aconfiguration address space, a memory address space, an input/outputaddress space, and a message address space. Memory space transactionsinclude one or more of read requests and write requests to transfer datato/from a memory-mapped location. In one embodiment, memory spacetransactions are capable of using two different address formats, e.g., ashort address format, such as a 32-bit address, or a long addressformat, such as 64-bit address. Configuration space transactions areused to access configuration space of the PCIe devices. Transactions tothe configuration space include read requests and write requests.Message space transactions (or, simply messages) are defined to supportin-band communication between PCIe agents.

Therefore, in one embodiment, transaction layer 205 assembles packetheader/payload 206. Format for current packet headers/payloads may befound in the PCIe specification at the PCIe specification website.

Quickly referring to FIG. 3, an embodiment of a PCIe transactiondescriptor is illustrated. In one embodiment, transaction descriptor 300is a mechanism for carrying transaction information. In this regard,transaction descriptor 300 supports identification of transactions in asystem. Other potential uses include tracking modifications of defaulttransaction ordering and association of transaction with channels.

Transaction descriptor 300 includes global identifier field 302,attributes field 304 and channel identifier field 306. In theillustrated example, global identifier field 302 is depicted comprisinglocal transaction identifier field 308 and source identifier field 310.In one embodiment, global transaction identifier 302 is unique for alloutstanding requests.

According to one implementation, local transaction identifier field 308is a field generated by a requesting agent, and it is unique for alloutstanding requests that require a completion for that requestingagent. Furthermore, in this example, source identifier 310 uniquelyidentifies the requestor agent within a PCIe hierarchy. Accordingly,together with source ID 310, local transaction identifier 308 fieldprovides global identification of a transaction within a hierarchydomain.

Attributes field 304 specifies characteristics and relationships of thetransaction. In this regard, attributes field 304 is potentially used toprovide additional information that allows modification of the defaulthandling of transactions. In one embodiment, attributes field 304includes priority field 312, reserved field 314, ordering field 316, andno-snoop field 318. Here, priority sub-field 312 may be modified by aninitiator to assign a priority to the transaction. Reserved attributefield 314 is left reserved for future, or vendor-defined usage. Possibleusage models using priority or security attributes may be implementedusing the reserved attribute field.

In this example, ordering attribute field 316 is used to supply optionalinformation conveying the type of ordering that may modify defaultordering rules. According to one example implementation, an orderingattribute of “0” denotes default ordering rules are to apply, wherein anordering attribute of “1” denotes relaxed ordering, wherein writes canpass writes in the same direction, and read completions can pass writesin the same direction. Snoop attribute field 318 is utilized todetermine if transactions are snooped. As shown, channel ID Field 306identifies a channel that a transaction is associated with.

Link Layer

Link layer 210, also referred to as data link layer 210, acts as anintermediate stage between transaction layer 205 and the physical layer220. In one embodiment, a responsibility of the data link layer 210 isproviding a reliable mechanism for exchanging Transaction Layer Packets(TLPs) between two components a link. One side of the Data Link Layer210 accepts TLPs assembled by the Transaction Layer 205, applies packetsequence identifier 211, i.e. an identification number or packet number,calculates and applies an error detection code, i.e. CRC 212, andsubmits the modified TLPs to the Physical Layer 220 for transmissionacross a physical to an external device.

Physical Layer

In one embodiment, physical layer 220 includes logical sub block 221 andelectrical sub-block 222 to physically transmit a packet to an externaldevice. Here, logical sub-block 221 is responsible for the “digital”functions of Physical Layer 221. In this regard, the logical sub-blockincludes a transmit section to prepare outgoing information fortransmission by physical sub-block 222, and a receiver section toidentify and prepare received information before passing it to the LinkLayer 210.

Physical block 222 includes a transmitter and a receiver. Thetransmitter is supplied by logical sub-block 221 with symbols, which thetransmitter serializes and transmits onto to an external device. Thereceiver is supplied with serialized symbols from an external device andtransforms the received signals into a bit-stream. The bit-stream isde-serialized and supplied to logical sub-block 221. In one embodiment,an 8b/10b transmission code is employed, where ten-bit symbols aretransmitted/received. Here, special symbols are used to frame a packetwith frames 223. In addition, in one example, the receiver also providesa symbol clock recovered from the incoming serial stream.

As stated above, although transaction layer 205, link layer 210, andphysical layer 220 are discussed in reference to a specific embodimentof a PCIe protocol stack, a layered protocol stack is not so limited. Infact, any layered protocol may be included/implemented. As an example,an port/interface that is represented as a layered protocol includes:(1) a first layer to assemble packets, i.e. a transaction layer; asecond layer to sequence packets, i.e. a link layer; and a third layerto transmit the packets, i.e. a physical layer. As a specific example, acommon standard interface (CSI) layered protocol is utilized.

Referring next to FIG. 4, an embodiment of a PCIe serial point to pointfabric is illustrated. Although an embodiment of a PCIe serialpoint-to-point link is illustrated, a serial point-to-point link is notso limited, as it includes any transmission path for transmitting serialdata. In the embodiment shown, a basic PCIe link includes two,low-voltage, differentially driven signal pairs: a transmit pair 406/411and a receive pair 412/407. Accordingly, device 405 includestransmission logic 406 to transmit data to device 410 and receivinglogic 407 to receive data from device 410. In other words, twotransmitting paths, i.e. paths 416 and 417, and two receiving paths,i.e. paths 418 and 419, are included in a PCIe link.

A transmission path refers to any path for transmitting data, such as atransmission line, a copper line, an optical line, a wirelesscommunication channel, an infrared communication link, or othercommunication path. A connection between two devices, such as device 405and device 410, is referred to as a link, such as link 415. A link maysupport one lane—each lane representing a set of differential signalpairs (one pair for transmission, one pair for reception). To scalebandwidth, a link may aggregate multiple lanes denoted by xN, where N isany supported Link width, such as 1, 2, 4, 8, 12, 16, 32, 64, or wider.

A differential pair refers to two transmission paths, such as lines 416and 417, to transmit differential signals. As an example, when line 416toggles from a low voltage level to a high voltage level, i.e. a risingedge, line 417 drives from a high logic level to a low logic level, i.e.a falling edge. Differential signals potentially demonstrate betterelectrical characteristics, such as better signal integrity, i.e.cross-coupling, voltage overshoot/undershoot, ringing, etc. This allowsfor better timing window, which enables faster transmission frequencies.

In some implementations, a high-performance interconnect andcorresponding interconnect protocol (e.g., such as a next generationPCIe-based interconnect) may be provided that is capable of operating athigh speeds such as 25 GT/s and/or 32 GT/s. In one example, two speedsmay be defined for the high performance interconnect, one at 25 GT/s and32 GT/s, based on the characteristics determined for the channel (e.g.,during link training). The interconnect, in one implementation, may bebackwards compatible with existing PCIe generations and speeds providedfor these generations (e.g., 8 GT/s, 16 GT/s, etc.).

Turning to the diagram 500 of FIG. 5, an example link training statemachine is shown, such as the PCIe link training and status statemachine (LTSSM). Transitions between the various link states may bedefined, including the signaling that is to take place to notify theother system on the link or to complete a handshake between theinterconnected devices to request, negotiate, and/or confirm thetransition from on state to the next in order to reach an active,transmitting link state (e.g., L0 (520)). For instance, some statetransitions may be defined to involve the sending and receiving oftraining set (TS) ordered sets (OSes). In an implementation utilizingPCIe as the PHY protocol, the TS ordered sets may include a TS1 and aTS2 ordered set, among other example ordered sets. The ordered sets andtraining sequences sent during link training may be based on theparticular link training state, with various link training statesutilized to accomplish corresponding link training activities andobjectives.

In one example, such as illustrated in FIG. 5, a link training statemachine 500 may include such states as a Reset state, a Detect state 505(e.g., to detect a far end termination (e.g., another device connectedto the lanes), a Polling state 510 (e.g., to establish symbol lock andconfigure lane polarity), a Configuration (or “Config”) state 515 (e.g.,to configure the physical lanes of a connection into a link withparticular lane width, lane numbering, etc., performing lane-to-lanedeskew and other link configuration activities), a Loopback state 535(e.g., to perform testing, fault isolation, equalization, and othertasks), a Recovery 540 state (e.g., for use to change the data rate ofoperation, re-establish bit lock, Symbol lock or block alignment,perform lane-to-lane de-skew, etc.) among other states (e.g., low powerstates L1 (525) and L2 (530)), which may be utilized to bring the linkto an active link state (e.g., L0 (520)). In one example, trainingsequences to be sent in a particular one (or more) of the link trainingstates (e.g., illustrated in the example of FIG. 5) may be defined toaccommodate the negotiation of a particular one of the supportedprotocols of a particular device. For instance, the particular trainingstate may be a training state preceding entry into an active link state(e.g., 520), or a training state in which the data rate may be upscaled(e.g., beyond that supported by at least one of the supportedprotocols), such as a PCIe state where a data rate transitions from aGen1 speed to Gen3 and higher speeds, among other examples.

In some implementations, additional link states may be defined (andcorresponding hardware circuitry and other logic implemented on devicescompatible with the interconnect protocol) to support testing of portson the device. For instance, additional states may be defined, which maybe entered to support testing of individual lanes (i.e., the hardwareand logic by which the device is to send and receive data on a givenbidirectional lane). In such instances, a link state machine (such asthe example link state machine introduced in FIG. 5) may be augmented toallow state transitions to deviate from those expected in training alink to a default, or standard operational state, to allow the lane tobe tested to transition to a first state, while other lanes of themulti-lane link to be transitioned to a different state to support thetesting of the lane under test.

In some instances, traditional tester devices, such as traditionalBERTs, may only test a single lane and devices may be programmed ordesigned (for various reasons) to limit the lanes which may be tested.For instance, traditional PCIe BERTs may only be able to test Lane 0 ofPCIe devices (e.g., due to other, competing transmitter equalizationconsiderations) and may be further limited in being able to only useexisting PCIe LTSSM transitions. For instance, a traditional BERT maytrain the DUT to L0 (e.g., resulting in a Lane 0 dependency), performsequalization through Recovery, transition from Recovery to Loopback(with the BERT as master), and then proceed with the test of thereceiver.

Additionally, in some traditional implementations, a tester may not useor cause real (near-end or far-end) cross-talk to be generated from theother lanes (not under test), but may rather model hypothetical (and inmany cases, worst case) cross-talk (e.g., combined near-end and far-endcrosstalk) using an approximation in the BERT to artificially injectextra noise into the signals sent on the lane under test during thetest. However, with interconnects being designed to handle increasingdata rates such as 32.0 GT/s (e.g., PCIe Gen4), it may be more criticalto test for precise package- and channel-introduced cross-talk byaccurately capturing real cross-talk resulting from the actual design ofthe package instead of relying on approximations as higher data ratesallow decreasingly small margins for error. In some cases, multi-LaneBERTs may be provided, which may simplify test implementations involvingmore than one lane at a time, but such system may be prohibitivelyexpensive in some applications. A link training state machine (such asthat illustrated in the example of FIG. 5) may be instead augmented, andcorresponding logic provided in a compliance device, to allow for a morecost-effective and precise approach using traditional single-lane BERTdesigns. Indeed, in some implementations, not only can far-end crosstalk (FEXT) be captured (e.g., the cross-talk resulting from thetransmissions of a remote device to the device under test), but near-endcross-talk (NEXT) (e.g., the cross-talk resulting from the transmissionsof lanes other than the victim lane (e.g., the lane under test) on thedevice under test). For instance, these new test-enabling link statesmay allow NEXT to be captured from the other transmitters on the DUTand/or allow FEXT to be captured by allowing signals to be sent to thereceivers on other lanes on the device other test while the lane undertest remains in loopback and other states during testing by the BERT,among other example benefits and implementations.

In some implementations, link state logic may be augmented to supportnot only a default or standard link state machine and transitionsbetween states defined in the standard link state machine, but may alsosupport specialized test states, which may allow individual lanes of amulti-lane link to be tested using a test device (e.g., an on-diemargining tester, a standalone bit error rate tester (BERT) device,etc.), while other lanes of the link generate far-end and/or near endcross-talk. Using these specialized state and state machine transitions,far-end cross-talk (or FEXT) and near-end cross-talk (or NEXT) may begenerated on the lanes not under test to accommodate precision testingof the lane (or, in the case of multi-lane testers, lanes) under test.While traditional lane testing involved the injection of artificial, orsimulated, noise on data of the lane being tested, such simulated noiseis typically cast to model worst case scenarios, which may ignore theactual features of the port being tested (e.g., which may be equippedwith circuitry and components to assist in minimizing crosstalk on thedevice (making tests using simulated worst-case cross-talk overlypessimistic and unrealistic)). Accordingly, in some cases, specializedtesting link states may enable more realistic margin information athigher data rates (such as PCIe Gen 5 at 32.0 GT/s), as opposed to thetraditional approaches relying on emulated cross-talk.

In some implementations, a standard, or default, link training statemachine defined for an interconnect may be augmented to supportspecialized testing link states, which may enable a port to train a linksuch that different lanes of the link enter different states to allowsome lanes to be tested (e.g., by running the lane through link trainingand link state transitions expected in or defined for defaultoperation), while other lanes enter one of potentially multipledifferent states to provide real (rather than synthesized) cross-talkand enable multiple, authentic testing modes. In one example, a linktraining algorithm may be augmented to identify and select one or moreparticular lanes of a link that are to be tested by a testing device,such as a BERT. The selected lane may be driven by the tester deviceduring the test. The remaining lanes of the device under test (DUT) maybe self-trained or be placed into an idle or other quiet state while theBERT drives link training and status state machine (LTSSM) changes onthe lane it controls in connection with the test of the lane (or thelane under test (LUT)). In some implementations, the link may be placedinto a loopback state, initiated by the tester device (e.g., through aspecialized ordered set sent to the device under test by the testerdevice using the link). When the link goes to Loopback, in such anexample, the DUT may drive (modified) compliance pattern inLoopback.Entry on all the other lanes or stay in transmitter electricalidle on all other lanes (i.e., the other lanes not under test) based onthe training information sent by the tester device on the lane connectedto the tester device. In this manner, the DUT itself may be used togenerate cross-talk desired to completing a test of one more lanes(e.g., the corresponding receiver-transmitter pairs) of the DUT, whilethe tester device manages the specific lane it wants to test.Furthermore, the DUT may also be put in a state by the training with thetester device where all other receivers on the DUT may receiver trafficwithout impacting loopback on the lane under test by the tester device,among other examples, such as discussed below.

Turning to the simplified block diagrams 600 a-b of FIGS. 6A-6B, examplesystems are shown including an example computing device (e.g., 605) andan example testing device (e.g., 610 a,b). In the example of FIG. 6A, asingle lane bit error rate tester (BERT) device 610 a is shown, whichmay be used to connect to a single lane (e.g., 630 b) of a device undertest (e.g., 605) and perform various margining and other testing of thelane. In this example, the computing device 605 may include one or moredata processing cores (e.g., 615) and/or other data processingcircuitry, which may utilize a layered interconnect stack 620 (e.g., aPCIe, UPI, Ethernet, OpenCAPI, Gen-Z, or other layered interconnectstacks) to communicate with other devices over one or more interconnectlinks. The interconnect stack 620 may be implemented through logiccircuitry and other hardware (as well as, or alternatively, usingsoftware- and/or firmware-implemented logic) to support and implementeach one of the interconnect layers (e.g., physical layer, logical PHY,data link layer, transaction layer, protocol layer, etc.), including thegeneration and sending of units of data (e.g., packets, frames, flits,phits, etc.) defined for the interconnect. The interconnect stack 620may further enable the port(s) of the device to enter and transitionbetween various operational and link states defined for theinterconnect, including link training and testing states with definedordered sets, training sequences, handshakes, and other signalingdefined to enable two interconnected devices to orchestrate the trainingand transmission of data on a link according to a correspondinginterconnect protocol. Such logic may include state machine logicimplemented at least partially in logic circuitry or other hardware ofthe computing device 605.

Continuing with the example of FIG. 6A, interconnect stack logic 620 maybe augmented in some implementations to support additional test-specificlink states and link state transitions, such as introduced in thediscussion above. For instance, interconnect stack logic 620 implementedon the device 605 may include test mode support logic 625, implementedat least in part using hardware logic circuitry. The test mode logic 625may enable additional testing link states as well as govern transitionsto these test states and coordination of how the testing link states areapplied on which lanes (e.g., 630 a-d) during the test. Within thepresent disclosure, a “lane” may alternatively refer to the physicallanes which implement a link connecting two devices, or the respectivereceiver/transmitter pair and supporting logic (e.g., 630 a-d) on adevice (e.g., 605) which couples the device to a corresponding physicallane of the link.

In the example of FIG. 6A, a single lane BERT 610 a is shown, which cancouple to and test each one of a plurality of different lanesindividually. Test mode logic 625 can enable the specific lane to betested (e.g., 630 b) to be identified and cause this lane under test(i.e., the receiver/transmitter pair of the port of the device 605connected to the bidirectional lane coupling the device under test 605to the BERT device 610 a) to enter one of the testing link states (e.g.,a loopback, active transmitting link state, a link training state, etc.)in connection with a test of the lane. In some cases, the BERT 610 a maydirect which link state(s) the lane under test enters during the test.During the test, the test mode logic 625 may identify one or more otherlanes (i.e., other than the lane under test) that are to enter othertesting link states to support the BERT device's testing of the laneunder test. For instance, the test mode logic 625 may cause one or more(or all) of the lanes (e.g., 630 a,c,d) other than the lane under test(e.g., 630 b) to enter link states to enable these lanes to producenear-end and/or far-end cross-talk on the victim lane under test (e.g.,630 b).

In some implementations, lanes other than the lane under test may remainunconnected, connected to a utility device (e.g., separate from, butsupporting the BERT), or connected to the BERT itself. In someimplementations, as shown in the example of FIG. 6B, a tester device(e.g., a multilane BERT device (e.g., 605 b)) may be provided withmultiple lanes (e.g., receiver/transmitter pairs) to connect to multiplelanes of a device under test. A multilane tester (e.g., 610 a-b) mayconnect to each one of the lanes (e.g., 630 a-d) of the device undertest (605). A multi-lane tester may test each lane of the device undertest serially, without any need for reconnection of the lanes.Additionally, the multi-lane tester may work in concert with the testmode logic 625 on the device under test 605 to assist in the generationof FEXT and NEXT on those lanes not currently under test usingsupporting testing link states, among other example implementations.

Turning to the diagram 700 of FIG. 7, a simplified block diagram 700 isshown illustrated a portion of a diagram of an augmented link statemachine showing specialized testing link states (e.g., 705, 710, 715,720), which may be added to the state machine to facilitate testing ofindividual lanes of a link. For instance, in the example of FIG. 7, theaugmented state machine may be an augmented version of a PCIe link statemachine, such as introduced in the diagram 500 of FIG. 5. For instance,standard link states defined for the state machine (e.g., in accordancewith a corresponding interconnect protocol) may include a receiverdetect state (e.g., 505), polling state (e.g., 510), configuration state(e.g., 515), and potentially other link training states which may beentered and used prior to transitioning to active, transmitting, oroperational link states (e.g., an L0 state (not shown), among otherexample states. During training of a link, various ordered sets, such astraining sequences (e.g., PCIe TS1 or TS2 training sequences) may besent, which may include fields which are encoded to provide informationspecific to the link training state and define various aspects of thelink (e.g., lane numbering, deskew, synchronization, bit lock,configuration, etc.). In some implementations, a link may be trainedeffectively lane-by-lane, with each receiver-transmitter pair sendingand receiving its own instances of the training sequences to configureand train each lane to the desired parameters to allow complete andreliable training of the overall link. As an example, symbol lock, bitlock, and block alignment may be accomplished on a per-lane basis, withthe training sequences sent on each lane adapted for achieving thecorrect configuration for the lane. In some cases, ordered sets of asame type may be sent synchronously on each lane in the link (althoughvalues in each ordered set may vary from lane to lane), among otherexamples.

In the example of FIG. 7, one or more fields of training sequences sentduring one or more of the link training states defined in standardstates of a link state machine may be augmented to provide an indicationthat the device participating in the training is to enter a testingmode. For instance, bits in one or more symbols of a training sequencesent in a particular, defined state or substate of the state machine maybe defined to communicate that the device is to be tested. Further, oneor more bits or fields in a training sequence may be defined to indicatethat a tester device (e.g., a BERT) is connected to one or more lanes ofthe link and that these lanes are to be tested. Further, one or morebits or fields of the same (or a different or subsequent instance ofthe) training sequence may be encoded with information to indicate thatother lanes, not under test, should transition to other testing linkstates to assist in facilitating the testing of a particular lane.Moreover, in connection with the identification of a particular lanethat is to be tested, a training sequence may be encoded to indicatethat the particular lane to be tested is to enter another link state,consistent with the type of test that is to be performed, among otherexamples.

In one example implementation, a tester device may encode a trainingsequence sent during a polling state (e.g., 510) (or another particularlink training state as defined in an interconnect protocol) to indicatethat a particular lane of the link is to be tested and that otherremaining lanes of the link are to transition to another testing linkstate to support the testing of the particular lane. Accordingly, ratherthan having all of the lanes transition together from the polling state510 to the next standard link training state (e.g., a configurationstate 515), the augmented fields of the training sequence may cause thedevice under test to transition the lane under test to a particular laneunder test link state (e.g., 705), while transitioning the remaininglanes to another testing link state (e.g., 710, 715, 720) that supportstesting of the lane under test and, in some cases, produces realcross-talk on the lane under test for use in various tests of the laneunder test (LUT) conducted by the tester device (e.g., a single lane ormultilane BERT).

In some instances, testing link states (e.g., 705, 710, 715, 720) may bebased on or incorporate one or more of the standard link states (e.g.,an active link state or loopback link state, among other examples).Indeed, in some cases, the tester device may interact with theparticular lane to simulate the operation of the receiver/transmitterconnected to the particular lane as it would transition from state tostate within the standard link state machine. For instance, the testerdevice may act as the loopback master within a loopback state or maysend signals, during the test, as defined in the standard link trainingmachine to cause the lane under test to transition between standard linktraining states. Even in cases where the LUT test state (e.g., 705) maymimic or include a standard link state, the transition to this linkstate or sub-state during testing may differ from transitions defined inthe standard link training machine. For instance, because the LUT teststate 705 only involves a test of a single lane, activities involved intraining all of the lanes to enter the state (during typical linktraining and state machine transitions) may be skipped. For instance,activities such as lane numbering, lane-to-lane deskew, and others maybe skipped, which may even allow entire intermediate link trainingstates to be skipped. In other cases, the activities and signalingwithin a LUT test state 705 and testing link states (e.g., 710, 715,720) for the remaining lanes (not under test) may be entirely differentfrom states defined in the standard link state machine, in addition todifferences in transitioning to these testing link states (e.g., fromthe polling state 510). For instance, the LUT test state 705 may bedictated entirely by the tester device (e.g., a BERT), with the testerdevice free to send any variety of signals to simulate variousconditions, state transitions, states, etc. as is desirable inconnection with a particular test, while the other testing link states(e.g., 710, 715, 720) cause the remaining lanes of the link to inject(or not inject) crosstalk onto the lane under test.

In the example of FIG. 7, some of the testing link states may includestates such as shown in the example diagram 700. For instance, onetesting link state 710 may be adapted to cause near-end cross-talk(NEXT) to be generated on the lanes under than the lane under test. Inanother example, a testing link state (e.g., 715) may be adapted togenerate only far-end cross-talk (FEXT) (while the transmitters of thereceiver/transmitter pairs of the lanes not under test remain quiet). Instill another example, a testing link state (e.g., 720) may generateboth NEXT and FEXT using the lanes not under test, among other examples.For instance, multiple versions of NEXT (e.g., 710), FEXT-only (e.g.,715), and NEXT/FEXT testing link states (e.g., 720) may be provided andsupported by the internal hardware and/or software logic of the deviceto be tested. For instance, varying types of stress signals may be sentwithin different testing link states to generate corresponding types ofthe cross-talk, such as cross-talk of varying severity (e.g., amplitudeand frequency), intermittent or continuous cross-talk, among otherexamples.

In some instances, to enable some testing link states, additionaldevices may be provided in connection with a tester device (e.g., 610),such as signal generators (e.g., to generate far-end cross-talk) or, asillustrated in the example block diagram 800 of FIG. 8, a compliancefixture device 805, among other examples. In the example of FIG. 8, acompliance fixture device 805 is provided, which may allow a connectionfor lanes not under test (i.e., the corresponding receiver/transmitterpairs) in the case of a single lane BERT 610. An example passivecompliance fixture device 805 may be used in addition to or inconnection with the single-lane BERT 610 to assist in facilitating oneor more test modes. In one example, the compliance fixture device 805may connect to each of the lanes of a link (i.e., including the lanethat is to be tested by the BERT 610) and facilitate test modesinvolving the collection of lanes, as well as enable the tester device610 to selectively connect to any one of the lanes through a mechanismin the compliance fixture device 805, such as through jumper cables, adip switch, or other circuitry. A compliance fixture device 805 may thusenable the tester device 610 to connect to any particular lane (e.g., toserially perform single lane tests of each of the lanes of the deviceunder test 605) while connecting the transmitters of each of theremaining lanes of the DUT 605 to another endpoint (e.g., on thecompliance fixture 805). Additionally, in some implementations, thecompliance fixture 805 may be configured to act in a loopback mode forall lanes other than the lane under test (e.g., 810). In this manner,the compliance fixture 805 may effectively cause the transmitters ofeach one of the lanes not under test to be connected to thecorresponding receivers of the same receiver/transmitter pair to put any(or all) of these other lanes into a self-loopback (such as illustratedin FIG. 8), among other example implementations. In otherimplementations, the functionality of the example compliance fixturedevice 805 illustrated in FIG. 8 may be integrated within a multi-laneBERT device or other tester device, among other alternativeimplementations.

Turning to the examples illustrated by the block diagrams 900 a-e ofFIGS. 9A-9E, various testing modes are illustrated utilizingcorresponding testing link states supplementing a standard link statemachine of an interconnect. For instance, in the example of FIG. 9A, acomputing device 605 including receiver/transmitter pairs (andsupporting logic) (e.g., 630 a-630) to implement bi-directional lanes ofa multi-lane link may connect to a tester device 610. The tester devicemay be a standalone tester, such as a BERT used in validation testing,or a tester device implemented on-die or otherwise within the samecomputing system as the device 605, among other examples. In the exampleof FIG. 9A, training sequences may be sent in a preceding link state(e.g., a polling link state) to indicate that the device 605 isconnected to a tester device and is to enter a particular test mode. Inthis example test mode, one of the lanes (e.g., 630 c) is to be testedby the tester device 610 and enter a state in which normal operation ofthe lane 630 c is to be simulated in connection with the test. In thisexample, the lanes not under test (e.g., 630 a,b,d,e) are to remainquiet (e.g., so as not to generate crosstalk). As the lane under test630 c is the only receiver connected to another device (e.g., 610) andreceiving the training sequences, only the receiver ofreceiver/transmitter pair 630 c receives the training sequence. Testmode support logic may identify the training sequence(s) requestingentry into the particular test mode and may cause bothreceiver/transmitter pair 630 c to enter a link under test state and theremaining receiver/transmitter pairs (e.g., 630 a,b,d,e) to enteranother different testing link state in accordance with the identifiedtest mode. In this example, the remaining receiver/transmitter pairs(e.g., 630 a,b,d,e) are caused to enter a testing link state in which nodata is transmitted by the respective transmitters of thereceiver/transmitter pairs (e.g., 630 a,b,d,e) and all signals are to beignored by the receivers of the remaining receiver/transmitter pairs(e.g., such that the protocol stack logic of the receiver/transmitterpairs (e.g., 630 a,b,d,e) do not inadvertently interpret noise on theirrespective lane as a legitimate signal defined according to the protocolstack).

In some implementations, training sequences that are sent from thetester device 610 to the device under test 605 may not only identifythat a particular lane is to be tested (e.g., the lane receiving thespecialized training sequence), but may explicitly identify a particularone of a set of test modes. For instance, a binary code may be injectedin one or more fields of the specialized training sequence (e.g., in anotherwise reserved field in a particular symbol sent in a trainingsequence within a particular link training state (e.g., a pollingstate)) to identify a specific one of multiple supported test modes.From this encoding, the device under test 605 may identify map theparticular identified test mode to one of a set of testing link statesdefined in an augmented link state machine and cause the remaining lanesto enter this testing link state in support of the identified test mode.In other implementations, rather than explicitly identifying a definedtest mode (e.g., through encodings in a specialized training sequence),the tester device 610 may instead implicitly identify a test mode byproviding an encoding to identify the testing link state(s) that thelanes of the device under test 605 are to enter in support of a testrequested by the tester device 605. For instance, in one exampleimplementations, the training sequences may identify a LUT testing linkstate in which the lane under test is to enter and may separatelyidentify one of the supporting testing link states that the remaininglanes (not under test) are to enter. In other implementations, theencoding within the training sequence may identify that a particularlane is to be tested and may only explicitly identify the supportingtesting link state that the remaining lanes (not under test) are toenter, among other example implementations. Indeed, it should beappreciated that a variety of different signals (e.g., ordered sets,training sequences, etc.) may be utilized to communicate a request to adevice under test to enter a particular test mode. Various encodingsincluding various information and encoded within various symbols,fields, slots, etc. may be adopted in various implementations withoutdeparting from the more generalized concepts presented herein.

Turning to the example of FIG. 9B, another example test mode isillustrated. As in other examples, such as that illustrated in FIG. 9A,the tester device 610 may send a signal to the receiver of a particularlane (e.g., 630 c) that is to be tested and identify (explicitly orimplicitly) that a particular test mode (defined or undefined) is to beentered. The receiver of the receiver/transmitter pair of lane 630 c mayidentify, from the signal, that the remaining lanes (e.g., 630 a,b,d,e)are to enter a particular one of multiple testing link states in orderto support the test requested by the tester device 610. Similarly, inthe examples of FIGS. 9C-9E, corresponding signals may be received bythe device 605 from the tester device 610 (at the lane under test) tocause the device 605 to transition the remaining lanes (not under test)to a corresponding testing link state (as will be described in moredetail in the examples below). In the case of the example of FIG. 9B,the remaining lanes are forced to transition to a testing link statethat causes the transmitters of the receiver/transmitter pairs of theseremaining lanes to generate near-end crosstalk (NEXT) on the victim laneunder test 630 c. This may be done by the receiver/transmitter pairs ofthe remaining lanes transmitting stress data on their transmitters.Further, in this example (as in the example testing state of FIG. 9A),the receivers of these receiver/transmitter pairs may ignore all signalsthat are received in this testing link state (e.g., to avoidmisinterpreting noise that may be received at these receiver/transmitterpairs).

Turning to the example of FIG. 9C, another example testing link statemay be provided, which allows both NEXT and FEXT to be generated usingthe lanes not under test. In one example, such a testing link state maybe implemented by looping back stress data generated at the transmittersof the receiver/transmitter pairs of the lanes not under test (e.g., 630a,b,d,e). In the example of FIG. 9C, a compliance fixture device 805 maybe utilized to facilitate the looping back of the stress data generatedat the transmitters of the receiver/transmitter pairs of the lanes notunder test, which causes both NEXT and FEXT to be exhibited on the laneunder test. As the testing link states may coexist with the standardlink states defined in a link state machine of a protocol (e.g., suchthat these lanes may later exit the testing link state and transitionbetween standard link states in normal (i.e., non-testing) operation),the risk exists that stress data transmitted to the receivers of thereceiver/transmitter pairs of the lanes not under test may beinadvertently match other signals defined within the protocol, which areto prompt some other (e.g., non-testing) action on the part of theprotocol stack logic of these receiver/transmitter pairs (e.g., atransition to another (e.g., non-testing) link state, performance of aparticular link training function, etc.). Accordingly, within testinglink states, in which receivers of the receiver/transmitter pairs of thelanes not under test are to receive stress data, protocol stack logic ofthese receiver/transmitter pairs may effectively ignore the substance orcontent of these stress signals while in these testing link states, suchthat the testing link state is not inadvertently exited or otherwiseinterrupted.

While the example of FIG. 9C shows the use of a compliance fixturedevice 805 to facilitate a NEXT/FEXT loopback state, otherimplementations may use other devices (including the tester deviceitself, such as in a multi-lane BERT) to facilitate the loopback of thestress data. In this example, the compliance fixture may further act asa retimer, redriver, repeater, or other data forwarding device to simplyforward data to and from the lane under test and the single lane tester(e.g., 610). For instance, the compliance fixture may utilizingswitching or multiplexing circuitry to identify that the tester istesting a particular one of the lanes (e.g., 630 c), such that dataforwarding is enabled for this lane, while loopback or transmittingmodes are enabled for the remaining lanes of the compliance fixturedevice (i.e., to connect to the corresponding receivers of the device's605 receiver/transmitter pairs (e.g., 630 a,b,d,e) connected to thelanes not under test.

In yet another example, illustrated in FIG. 9D, other testing linkstates may cause only far-end crosstalk to be generated using theremaining lanes not under test. For instance, stress signals may begenerated at another device, such as a signal generator device (e.g.,905), and sent to the receivers of the receiver/transmitter pairs of thelanes not under test (e.g., 630 a,b,d,e). In this example testing linkstate, the transmitters of the receiver/transmitter pairs of the lanesnot under test may be placed in an idle mode, such that no data isdeliberately transmitted to generate NEXT on the lane under test (e.g.,630 c). Additionally, as in the example of FIG. 9C (and other testinglink states where lanes not under test are to receive stress data duringa test of the lane under test), the receivers of thereceiver/transmitter pairs (e.g., 630 a,b,d,e) not under test may ignorethe stress data generated by the signal generators 905. In someimplementations, signal generators (e.g., 905) used in a test of aparticular lane (e.g., 630 c) may be coupled with and driven by thetester device 610, such that the tester device 610 selects which stresssignals are sent by the signal generator(s) (e.g., 905) on which lanes,at which times, and at what intervals (e.g., to achieve specificobjectives of the test administered by the tester device (which may beselected, programmed, and otherwise defined using a software interfaceby a human user or other system)). In other instances, signal generatorsor other supplemental devices may be additionally used to support othertesting link states, such as NEXT/FEXT testing link states where stressdata is to be both transmitted and received on lanes not under test bythe device 605. In such instances, the signal generator(s) may includereceivers to receive (e.g., and effectively ignore and dispose of)stress signals sent from the transmitters of the receiver/transmitterpairs (e.g., 630 a,b,d,e) not under test, among other examples.

In the examples of FIGS. 9A-9D, a single lane tester device was shown.However, in some implementations, a multi-lane tester device may beprovided. Accordingly, additional testing link states may be added andsupported by devices (e.g., 605) in addition to testing link statesspecific to single lane testers. In some cases, such as illustrated inthe example of FIG. 9E, the same testing link states used with singlelane testers may be used to support testing using multilane testers.Indeed, a multilane tester may simplify the implementation of varioustest modes (which might otherwise make use of supplemental devices suchas compliance fixtures (e.g., 805), signal generators (e.g., 905), etc.For instance, in the example of FIG. 9E, a multilane BERT (e.g., 610)may natively provide the functionality provided by such supplementaldevices. For instance, in the example of FIG. 9E, the multi-lane testerdevice may enable a NEXT/FEXT testing link mode where the tester devicereceives stress data generated by and transmitted from the transmittersof the lanes not under test on the device 605. In other implementations,the multi-lane tester device 610 may participate in a loopback-basedNEXT/FEXT testing link state (e.g., similar to the testing link stateillustrated in the example of FIG. 9C). In some cases, the multi-lanetester device may either act as the master or the slave in theloopback-based NEXT/FEXT testing link state, with some testing linkstates defined to have the transmitters of the device under testgenerating the stress signals on the non-tested lanes to be looped-backthrough the tester device, and alternative testing link states definedto have the transmitters of the multi-lane tester generate the stresssignals on the non-tested lanes to be looped-back through thecorresponding receiver/transmitter pairs of the device under test 605. Amulti-lane tester device may also be used in a FEXT-only testing linkstate to generate the stress signals for delivery to the receivers ofthe receiver/transmitter pairs of the non-test lanes (e.g., in place ofseparate, dedicated signal generators (e.g., 905) such as in the exampleof FIG. 9D), among other example uses.

While the examples of FIGS. 9A-9E each show the same lane (e.g., 630 c)serving as the lane under test, it should be appreciated that this isshown merely for ease of illustrating variations between differenttesting link state examples. Indeed, any one of the multiple lanes(i.e., receiver/transmitter pairs (e.g., 630 a-e)) may be connected to atester device (e.g., a single lane BERT) and be the subjectlane-under-test. Further, any one of the multiple lanes, depending onthe test, may either enter a LUT testing link state (and be the laneunder the test) or enter a supporting testing link state to generatecross talk on the selected lane under test. Accordingly, the protocolstack logic implemented at a respective receiver/transmitter pair (e.g.,630 a-e) may support, not only the standard link states defined for theprotocol, but also supplemental or added testing link states to allowthe lane to be tested as the lane under test or to support the testingof another one of the lanes through the generation of cross-talk on thelane under test.

As introduced above, principles and aspects of a standard link statemachine and corresponding logic may be leveraged, in some examples, tofacilitate transitions to specialized testing link states, such as thoseintroduced above. As an illustrative example, a tester device, such as aBERT including protocol stack logic to allow the BERT to be at leastpartially protocol-aware to send and interpret signals defined within aparticular protocol supported by a device under test, may guide thedevice under test through various protocol-defined flows during a test.For instance, within a LUT testing state, the BERT may guide the deviceunder test through an active L0 link state (e.g., skipping aconfiguration link state), to a Recovery link state (including, in somecases, equalization), through to a Loopback link state, and so on asprogrammed in accordance with a particular test. In such instances, theBERT may utilized protocol-defined messaging to facilitate these testtransitions between the standard link states.

In a more detailed example, and returning to the illustration 700 inFIG. 7, a device that is to have one or more of its receiver/transmitterpairs tested by a tester device may first have each of itsreceiver/transmitter pairs, corresponding to a multilane link, enter areceiver Detect state 505. All lanes may detect another device (e.g.,due to self-Loopback or connection to the BERT or connection to 50 ohmterminations or other test equipment or sources with 50 ohmterminations) in order to progress past the Detect state. In otherimplementations, the device under test may simply detect an exit from anElectrical Idle state (e.g., in which the device is placed inpreparation for the test) due to the tester device driving an electricalpattern to the lane under test. Protocol-defined requirements for thistransition may be further relaxed in some implementations to force eachof the lanes not connected to a tester device to continue with linktraining in spite of not detecting a connected receiver on the other endof the lane during a Detect state 505 (e.g., in a case of a NEXT-onlytesting link state, such as in the example of FIG. 9C).

Continuing with this example, the port that includes the lane under testmay exit a Detect state 505 to enter a Polling state 510. In this state,the tester device may send a modified training sequence (e.g., TS1/TS2Ordered Sets through Polling.Active and Polling.Configuration) with oneor more bits set (e.g., in Symbol 5 of the training sequence) toindicate a test mode that is to be entered involving the remaining lanesentering a particular testing link state. In one example, lanes thatdetect a receiver (during Detect 505) may train (e.g., with their own(looped back) TS1/TS2 Ordered Sets) when not connected to the testerdevice. In other cases, the lanes not under test may be configured tosimply ignore all traffic either at the direction of the link-wideprotocol stack logic (based on receiving the training sequence on theBERT-connected lane to indicate that the link is in a test mode) or bydefault after a certain timeout period (e.g., the timeout based onfailing to receive further training data on the lanes not connected tothe tester device), among other examples. In some implementations, thePolling itself may be modified to accommodate transitions to the testinglink states.

In the example, where a single-lane tester device is used, the modifiedtraining sequences indicating a testing mode would be sent only to thereceiver of the receiver/transmitter pair to be tested. When thereceiver/transmitter pair corresponding to the lane under test receivesthe modified training sequence(s) (e.g., TS1/TS2 Ordered Sets in aPolling state), the receiver/transmitter pair logic may instruct thedevice link state machine logic (e.g., LTSSM logic) to transition thelane under test to a LUT link testing state and the remaining lanes tosupporting testing link states. In one example, the LUT testing linkstate may include or mimic an L0 state. Accordingly, in such examples,intermediate states (e.g., a Configuration state 515) that wouldnormally be entered prior to entering the L0 state may be skipped by thelink state machine logic. For instance, the Configuration state may beskipped to enter the L0 state (e.g., 520) to begin operation within theLUT testing state (e.g., on receipt of the modified TS2 Ordered Setswith bits set to indicate a corresponding test mode). Aspect of the linkthat would be trained during the skipped link training states may be setto default values (e.g., the lane number assignment may be the defaultlane number, among other examples).

Continuing with this example, the LUT testing state (or sequence ofsteps) may involve driving the lane under test to a Loopback state.Referring to FIG. 5, entering Loopback state 535 may involve firsttransitioning to a Recovery state 540. In one example implementing aPCIe-based interconnect, if the device under test is a Down Stream Port(DSP), the transition from L0 520 to Recovery 540 with equalization isinitiated by the device under test (with bypass mechanisms as defined)at all relevant data rates and the tester device follows. In cases wherethe device under test is an Up Stream Port (USP), the tester device mayinitiate the transition from L0 to Recovery with equalization (withbypass mechanisms as defined) at all relevant data rates, with thedevice under test following. Upon existing the Recovery state 540, thetester device (in a LUT testing state) may initiate the transition toLoopback 535 as Loopback master. The device under test, then, entersLoopback 535 as slave, with Loopback bit set on one Lane. FromLoopback.Entry, all Lanes in Slave mode that did not receive themodified TS1/TS2 Ordered Sets during the Polling state 510 may send outa compliance pattern (or modified compliance pattern), among otherexample implementations. With the lane under test in Loopback, thetester device can then perform measurements on the lane under test andgenerate results describing the performance of the receiver/transmitterpair on the device under test corresponding to the lane under test.

The foregoing disclosure has presented a number of example testing linkstates, which may supplement standard link states defined in aninterconnect protocol. It should be appreciated that other testing linkstates may be provided in addition to those identified above withoutdeparting from the more generalized principles contained within thisdisclosure. For instance, while some of the example state machines andordered sequences discussed herein were described with reference to PCIeor PCIe-based protocols, it should be appreciated that similar,corresponding enhancements may be made to other interconnect protocols,such OpenCAPI™, Gen-Z™, UPI, Universal Serial Bus, (USB), Cache CoherentInterconnect for Accelerators (CCIX™), Advanced Micro Device™'s (AMD™)Infinity™, Common Communication Interface (CCI), or Qualcomm™'s Centrig™interconnect, among others.

Note that the apparatus', methods', and systems described above may beimplemented in any electronic device or system as aforementioned. Asspecific illustrations, the figures below provide exemplary systems forutilizing the invention as described herein. As the systems below aredescribed in more detail, a number of different interconnects aredisclosed, described, and revisited from the discussion above. And as isreadily apparent, the advances described above may be applied to any ofthose interconnects, fabrics, or architectures.

Referring to FIG. 10, an embodiment of a block diagram for a computingsystem including a multicore processor is depicted. Processor 1000includes any processor or processing device, such as a microprocessor,an embedded processor, a digital signal processor (DSP), a networkprocessor, a handheld processor, an application processor, aco-processor, a system on a chip (SOC), or other device to execute code.Processor 1000, in one embodiment, includes at least two cores—core 1001and 1002, which may include asymmetric cores or symmetric cores (theillustrated embodiment). However, processor 1000 may include any numberof processing elements that may be symmetric or asymmetric.

In one embodiment, a processing element refers to hardware or logic tosupport a software thread. Examples of hardware processing elementsinclude: a thread unit, a thread slot, a thread, a process unit, acontext, a context unit, a logical processor, a hardware thread, a core,and/or any other element, which is capable of holding a state for aprocessor, such as an execution state or architectural state. In otherwords, a processing element, in one embodiment, refers to any hardwarecapable of being independently associated with code, such as a softwarethread, operating system, application, or other code. A physicalprocessor (or processor socket) typically refers to an integratedcircuit, which potentially includes any number of other processingelements, such as cores or hardware threads.

A core often refers to logic located on an integrated circuit capable ofmaintaining an independent architectural state, wherein eachindependently maintained architectural state is associated with at leastsome dedicated execution resources. In contrast to cores, a hardwarethread typically refers to any logic located on an integrated circuitcapable of maintaining an independent architectural state, wherein theindependently maintained architectural states share access to executionresources. As can be seen, when certain resources are shared and othersare dedicated to an architectural state, the line between thenomenclature of a hardware thread and core overlaps. Yet often, a coreand a hardware thread are viewed by an operating system as individuallogical processors, where the operating system is able to individuallyschedule operations on each logical processor.

Physical processor 1000, as illustrated in FIG. 10, includes twocores—core 1001 and 1002. Here, core 1001 and 1002 are consideredsymmetric cores, i.e. cores with the same configurations, functionalunits, and/or logic. In another embodiment, core 1001 includes anout-of-order processor core, while core 1002 includes an in-orderprocessor core. However, cores 1001 and 1002 may be individuallyselected from any type of core, such as a native core, a softwaremanaged core, a core adapted to execute a native Instruction SetArchitecture (ISA), a core adapted to execute a translated InstructionSet Architecture (ISA), a co-designed core, or other known core. In aheterogeneous core environment (i.e. asymmetric cores), some form oftranslation, such a binary translation, may be utilized to schedule orexecute code on one or both cores. Yet to further the discussion, thefunctional units illustrated in core 1001 are described in furtherdetail below, as the units in core 1002 operate in a similar manner inthe depicted embodiment.

As depicted, core 1001 includes two hardware threads 1001 a and 1001 b,which may also be referred to as hardware thread slots 1001 a and 1001b. Therefore, software entities, such as an operating system, in oneembodiment potentially view processor 1000 as four separate processors,i.e., four logical processors or processing elements capable ofexecuting four software threads concurrently. As alluded to above, afirst thread is associated with architecture state registers 1001 a, asecond thread is associated with architecture state registers 1001 b, athird thread may be associated with architecture state registers 1002 a,and a fourth thread may be associated with architecture state registers1002 b. Here, each of the architecture state registers (1301 a, 1001 b,1002 a, and 1002 b) may be referred to as processing elements, threadslots, or thread units, as described above. As illustrated, architecturestate registers 1001 a are replicated in architecture state registers1001 b, so individual architecture states/contexts are capable of beingstored for logical processor 1001 a and logical processor 1001 b. Incore 1001, other smaller resources, such as instruction pointers andrenaming logic in allocator and renamer block 1030 may also bereplicated for threads 1001 a and 1001 b. Some resources, such asre-order buffers in reorder/retirement unit 1035, ILTB 1020, load/storebuffers, and queues may be shared through partitioning. Other resources,such as general purpose internal registers, page-table base register(s),low-level data-cache and data-TLB 1015, execution unit(s) 1040, andportions of out-of-order unit 1035 are potentially fully shared.

Processor 1000 often includes other resources, which may be fullyshared, shared through partitioning, or dedicated by/to processingelements. In FIG. 10, an embodiment of a purely exemplary processor withillustrative logical units/resources of a processor is illustrated. Notethat a processor may include, or omit, any of these functional units, aswell as include any other known functional units, logic, or firmware notdepicted. As illustrated, core 1001 includes a simplified,representative out-of-order (OOO) processor core. But an in-orderprocessor may be utilized in different embodiments. The OOO coreincludes a branch target buffer 1020 to predict branches to beexecuted/taken and an instruction-translation buffer (I-TLB) 1020 tostore address translation entries for instructions.

Core 1001 further includes decode module 1025 coupled to fetch unit 1020to decode fetched elements. Fetch logic, in one embodiment, includesindividual sequencers associated with thread slots 1001 a, 1001 b,respectively. Usually core 1001 is associated with a first ISA, whichdefines/specifies instructions executable on processor 1000. Oftenmachine code instructions that are part of the first ISA include aportion of the instruction (referred to as an opcode), whichreferences/specifies an instruction or operation to be performed. Decodelogic 1025 includes circuitry that recognizes these instructions fromtheir opcodes and passes the decoded instructions on in the pipeline forprocessing as defined by the first ISA. For example, as discussed inmore detail below decoders 1025, in one embodiment, include logicdesigned or adapted to recognize specific instructions, such astransactional instruction. As a result of the recognition by decoders1025, the architecture or core 1001 takes specific, predefined actionsto perform tasks associated with the appropriate instruction. It isimportant to note that any of the tasks, blocks, operations, and methodsdescribed herein may be performed in response to a single or multipleinstructions; some of which may be new or old instructions. Notedecoders 1026, in one embodiment, recognize the same ISA (or a subsetthereof). Alternatively, in a heterogeneous core environment, decoders1026 recognize a second ISA (either a subset of the first ISA or adistinct ISA).

In one example, allocator and renamer block 1030 includes an allocatorto reserve resources, such as register files to store instructionprocessing results. However, threads 1001 a and 1001 b are potentiallycapable of out-of-order execution, where allocator and renamer block1030 also reserves other resources, such as reorder buffers to trackinstruction results. Unit 1030 may also include a register renamer torename program/instruction reference registers to other registersinternal to processor 1000. Reorder/retirement unit 1035 includescomponents, such as the reorder buffers mentioned above, load buffers,and store buffers, to support out-of-order execution and later in-orderretirement of instructions executed out-of-order.

Scheduler and execution unit(s) block 1040, in one embodiment, includesa scheduler unit to schedule instructions/operation on execution units.For example, a floating point instruction is scheduled on a port of anexecution unit that has an available floating point execution unit.Register files associated with the execution units are also included tostore information instruction processing results. Exemplary executionunits include a floating point execution unit, an integer executionunit, a jump execution unit, a load execution unit, a store executionunit, and other known execution units.

Lower level data cache and data translation buffer (D-TLB) 1050 arecoupled to execution unit(s) 1040. The data cache is to store recentlyused/operated on elements, such as data operands, which are potentiallyheld in memory coherency states. The D-TLB is to store recentvirtual/linear to physical address translations. As a specific example,a processor may include a page table structure to break physical memoryinto a plurality of virtual pages.

Here, cores 1001 and 1002 share access to higher-level or further-outcache, such as a second level cache associated with on-chip interface1010. Note that higher-level or further-out refers to cache levelsincreasing or getting further way from the execution unit(s). In oneembodiment, higher-level cache is a last-level data cache—last cache inthe memory hierarchy on processor 1000—such as a second or third leveldata cache. However, higher level cache is not so limited, as it may beassociated with or include an instruction cache. A trace cache—a type ofinstruction cache—instead may be coupled after decoder 1025 to storerecently decoded traces. Here, an instruction potentially refers to amacro-instruction (i.e. a general instruction recognized by thedecoders), which may decode into a number of micro-instructions(micro-operations).

In the depicted configuration, processor 1000 also includes on-chipinterface module 1010. Historically, a memory controller, which isdescribed in more detail below, has been included in a computing systemexternal to processor 1000. In this scenario, on-chip interface 1010 isto communicate with devices external to processor 1000, such as systemmemory 1075, a chipset (often including a memory controller hub toconnect to memory 1075 and an I/O controller hub to connect peripheraldevices), a memory controller hub, a northbridge, or other integratedcircuit. And in this scenario, bus 1005 may include any knowninterconnect, such as multi-drop bus, a point-to-point interconnect, aserial interconnect, a parallel bus, a coherent (e.g. cache coherent)bus, a layered protocol architecture, a differential bus, and a GTL bus.

Memory 1075 may be dedicated to processor 1000 or shared with otherdevices in a system. Common examples of types of memory 1075 includeDRAM, SRAM, non-volatile memory (NV memory), and other known storagedevices. Note that device 1080 may include a graphic accelerator,processor or card coupled to a memory controller hub, data storagecoupled to an I/O controller hub, a wireless transceiver, a flashdevice, an audio controller, a network controller, or other knowndevice.

Recently however, as more logic and devices are being integrated on asingle die, such as SOC, each of these devices may be incorporated onprocessor 1000. For example in one embodiment, a memory controller hubis on the same package and/or die with processor 1000. Here, a portionof the core (an on-core portion) 1010 includes one or more controller(s)for interfacing with other devices such as memory 1075 or a graphicsdevice 1080. The configuration including an interconnect and controllersfor interfacing with such devices is often referred to as an on-core (orun-core configuration). As an example, on-chip interface 1010 includes aring interconnect for on-chip communication and a high-speed serialpoint-to-point link 1005 for off-chip communication. Yet, in the SOCenvironment, even more devices, such as the network interface,co-processors, memory 1075, graphics processor 1080, and any other knowncomputer devices/interface may be integrated on a single die orintegrated circuit to provide small form factor with high functionalityand low power consumption.

In one embodiment, processor 1000 is capable of executing a compiler,optimization, and/or translator code 1077 to compile, translate, and/oroptimize application code 1076 to support the apparatus and methodsdescribed herein or to interface therewith. A compiler often includes aprogram or set of programs to translate source text/code into targettext/code. Usually, compilation of program/application code with acompiler is done in multiple phases and passes to transform hi-levelprogramming language code into low-level machine or assembly languagecode. Yet, single pass compilers may still be utilized for simplecompilation. A compiler may utilize any known compilation techniques andperform any known compiler operations, such as lexical analysis,preprocessing, parsing, semantic analysis, code generation, codetransformation, and code optimization.

Larger compilers often include multiple phases, but most often thesephases are included within two general phases: (1) a front-end, i.e.generally where syntactic processing, semantic processing, and sometransformation/optimization may take place, and (2) a back-end, i.e.generally where analysis, transformations, optimizations, and codegeneration takes place. Some compilers refer to a middle, whichillustrates the blurring of delineation between a front-end and back endof a compiler. As a result, reference to insertion, association,generation, or other operation of a compiler may take place in any ofthe aforementioned phases or passes, as well as any other known phasesor passes of a compiler. As an illustrative example, a compilerpotentially inserts operations, calls, functions, etc. in one or morephases of compilation, such as insertion of calls/operations in afront-end phase of compilation and then transformation of thecalls/operations into lower-level code during a transformation phase.Note that during dynamic compilation, compiler code or dynamicoptimization code may insert such operations/calls, as well as optimizethe code for execution during runtime. As a specific illustrativeexample, binary code (already compiled code) may be dynamicallyoptimized during runtime. Here, the program code may include the dynamicoptimization code, the binary code, or a combination thereof.

Similar to a compiler, a translator, such as a binary translator,translates code either statically or dynamically to optimize and/ortranslate code. Therefore, reference to execution of code, applicationcode, program code, or other software environment may refer to: (1)execution of a compiler program(s), optimization code optimizer, ortranslator either dynamically or statically, to compile program code, tomaintain software structures, to perform other operations, to optimizecode, or to translate code; (2) execution of main program code includingoperations/calls, such as application code that has beenoptimized/compiled; (3) execution of other program code, such aslibraries, associated with the main program code to maintain softwarestructures, to perform other software related operations, or to optimizecode; or (4) a combination thereof.

Referring now to FIG. 11, shown is a block diagram of another system1100 in accordance with an embodiment of the present invention. As shownin FIG. 11, multiprocessor system 1100 is a point-to-point interconnectsystem, and includes a first processor 1170 and a second processor 1180coupled via a point-to-point interconnect 1150. Each of processors 1170and 1180 may be some version of a processor. In one embodiment, 1152 and1154 are part of a serial, point-to-point coherent interconnect fabric,such as a high-performance architecture. As a result, the invention maybe implemented within the QPI architecture.

While shown with only two processors 1170, 1180, it is to be understoodthat the scope of the present invention is not so limited. In otherembodiments, one or more additional processors may be present in a givenprocessor.

Processors 1170 and 1180 are shown including integrated memorycontroller units 1172 and 1182, respectively. Processor 1170 alsoincludes as part of its bus controller units point-to-point (P-P)interfaces 1176 and 1178; similarly, second processor 1180 includes P-Pinterfaces 1186 and 1188. Processors 1170, 1180 may exchange informationvia a point-to-point (P-P) interface 1150 using P-P interface circuits1178, 1188. As shown in FIG. 11, IMCs 1172 and 1182 couple theprocessors to respective memories, namely a memory 1132 and a memory1134, which may be portions of main memory locally attached to therespective processors.

Processors 1170, 1180 each exchange information with a chipset 1190 viaindividual P-P interfaces 1152, 1154 using point to point interfacecircuits 1176, 1194, 1186, 1198. Chipset 1190 also exchanges informationwith a high-performance graphics circuit 1138 via an interface circuit1192 along a high-performance graphics interconnect 1139.

A shared cache (not shown) may be included in either processor oroutside of both processors; yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode.

Chipset 1190 may be coupled to a first bus 1116 via an interface 1196.In one embodiment, first bus 1116 may be a Peripheral ComponentInterconnect (PCI) bus, or a bus such as a PCI Express bus or anotherthird generation I/O interconnect bus, although the scope of the presentinvention is not so limited.

As shown in FIG. 11, various I/O devices 1114 are coupled to first bus1116, along with a bus bridge 1118 which couples first bus 1116 to asecond bus 1120. In one embodiment, second bus 1120 includes a low pincount (LPC) bus. Various devices are coupled to second bus 1120including, for example, a keyboard and/or mouse 1122, communicationdevices 1127 and a storage unit 1128 such as a disk drive or other massstorage device which often includes instructions/code and data 1130, inone embodiment. Further, an audio I/O 1124 is shown coupled to secondbus 1120. Note that other architectures are possible, where the includedcomponents and interconnect architectures vary. For example, instead ofthe point-to-point architecture of FIG. 11, a system may implement amulti-drop bus or other such architecture.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

A design may go through various stages, from creation to simulation tofabrication. Data representing a design may represent the design in anumber of manners. First, as is useful in simulations, the hardware maybe represented using a hardware description language or anotherfunctional description language. Additionally, a circuit level modelwith logic and/or transistor gates may be produced at some stages of thedesign process. Furthermore, most designs, at some stage, reach a levelof data representing the physical placement of various devices in thehardware model. In the case where conventional semiconductor fabricationtechniques are used, the data representing the hardware model may be thedata specifying the presence or absence of various features on differentmask layers for masks used to produce the integrated circuit. In anyrepresentation of the design, the data may be stored in any form of amachine readable medium. A memory or a magnetic or optical storage suchas a disc may be the machine readable medium to store informationtransmitted via optical or electrical wave modulated or otherwisegenerated to transmit such information. When an electrical carrier waveindicating or carrying the code or design is transmitted, to the extentthat copying, buffering, or re-transmission of the electrical signal isperformed, a new copy is made. Thus, a communication provider or anetwork provider may store on a tangible, machine-readable medium, atleast temporarily, an article, such as information encoded into acarrier wave, embodying techniques of embodiments of the presentinvention.

A module as used herein refers to any combination of hardware, software,and/or firmware. As an example, a module includes hardware, such as amicro-controller, associated with a non-transitory medium to store codeadapted to be executed by the micro-controller. Therefore, reference toa module, in one embodiment, refers to the hardware, which isspecifically configured to recognize and/or execute the code to be heldon a non-transitory medium. Furthermore, in another embodiment, use of amodule refers to the non-transitory medium including the code, which isspecifically adapted to be executed by the microcontroller to performpredetermined operations. And as can be inferred, in yet anotherembodiment, the term module (in this example) may refer to thecombination of the microcontroller and the non-transitory medium. Oftenmodule boundaries that are illustrated as separate commonly vary andpotentially overlap. For example, a first and a second module may sharehardware, software, firmware, or a combination thereof, whilepotentially retaining some independent hardware, software, or firmware.In one embodiment, use of the term logic includes hardware, such astransistors, registers, or other hardware, such as programmable logicdevices.

Use of the phrase ‘configured to,’ in one embodiment, refers toarranging, putting together, manufacturing, offering to sell, importingand/or designing an apparatus, hardware, logic, or element to perform adesignated or determined task. In this example, an apparatus or elementthereof that is not operating is still ‘configured to’ perform adesignated task if it is designed, coupled, and/or interconnected toperform said designated task. As a purely illustrative example, a logicgate may provide a 0 or a 1 during operation. But a logic gate‘configured to’ provide an enable signal to a clock does not includeevery potential logic gate that may provide a 1 or 0. Instead, the logicgate is one coupled in some manner that during operation the 1 or 0output is to enable the clock. Note once again that use of the term‘configured to’ does not require operation, but instead focus on thelatent state of an apparatus, hardware, and/or element, where in thelatent state the apparatus, hardware, and/or element is designed toperform a particular task when the apparatus, hardware, and/or elementis operating.

Furthermore, use of the phrases ‘to,’ ‘capable of/to,’ and or ‘operableto,’ in one embodiment, refers to some apparatus, logic, hardware,and/or element designed in such a way to enable use of the apparatus,logic, hardware, and/or element in a specified manner. Note as abovethat use of to, capable to, or operable to, in one embodiment, refers tothe latent state of an apparatus, logic, hardware, and/or element, wherethe apparatus, logic, hardware, and/or element is not operating but isdesigned in such a manner to enable use of an apparatus in a specifiedmanner.

A value, as used herein, includes any known representation of a number,a state, a logical state, or a binary logical state. Often, the use oflogic levels, logic values, or logical values is also referred to as 1'sand 0's, which simply represents binary logic states. For example, a 1refers to a high logic level and 0 refers to a low logic level. In oneembodiment, a storage cell, such as a transistor or flash cell, may becapable of holding a single logical value or multiple logical values.However, other representations of values in computer systems have beenused. For example the decimal number ten may also be represented as abinary value of 1010 and a hexadecimal letter A. Therefore, a valueincludes any representation of information capable of being held in acomputer system.

Moreover, states may be represented by values or portions of values. Asan example, a first value, such as a logical one, may represent adefault or initial state, while a second value, such as a logical zero,may represent a non-default state. In addition, the terms reset and set,in one embodiment, refer to a default and an updated value or state,respectively. For example, a default value potentially includes a highlogical value, i.e. reset, while an updated value potentially includes alow logical value, i.e. set. Note that any combination of values may beutilized to represent any number of states.

The embodiments of methods, hardware, software, firmware or code setforth above may be implemented via instructions or code stored on amachine-accessible, machine readable, computer accessible, or computerreadable medium which are executable by a processing element. Anon-transitory machine-accessible/readable medium includes any mechanismthat provides (i.e., stores and/or transmits) information in a formreadable by a machine, such as a computer or electronic system. Forexample, a non-transitory machine-accessible medium includesrandom-access memory (RAM), such as static RAM (SRAM) or dynamic RAM(DRAM); ROM; magnetic or optical storage medium; flash memory devices;electrical storage devices; optical storage devices; acoustical storagedevices; other form of storage devices for holding information receivedfrom transitory (propagated) signals (e.g., carrier waves, infraredsignals, digital signals); etc., which are to be distinguished from thenon-transitory mediums that may receive information there from.

Instructions used to program logic to perform embodiments of theinvention may be stored within a memory in the system, such as DRAM,cache, flash memory, or other storage. Furthermore, the instructions canbe distributed via a network or by way of other computer readable media.Thus a machine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer), but is not limited to, floppy diskettes, optical disks,Compact Disc, Read-Only Memory (CD-ROMs), and magneto-optical disks,Read-Only Memory (ROMs), Random Access Memory (RAM), ErasableProgrammable Read-Only Memory (EPROM), Electrically ErasableProgrammable Read-Only Memory (EEPROM), magnetic or optical cards, flashmemory, or a tangible, machine-readable storage used in the transmissionof information over the Internet via electrical, optical, acoustical orother forms of propagated signals (e.g., carrier waves, infraredsignals, digital signals, etc.). Accordingly, the computer-readablemedium includes any type of tangible machine-readable medium suitablefor storing or transmitting electronic instructions or information in aform readable by a machine (e.g., a computer).

In some embodiments, an electronic device may be configured to performone or more processes, techniques, and/or methods as described herein,or portions thereof. One such process is depicted in Figure X-2. Forexample, the process may include performing, by a first and secondretimer, an SKP adjustment during a first SKP ordered set (OS); andperforming, by a third and fourth retimer, an SKP adjustment during asecond SKP OS.

In some embodiments, an electronic device may be configured to performone or more processes, techniques, and/or methods as described herein,or portions thereof. For example, the process may include enhancing atraining ordered set (OS) to allow for five generations of speeds; andsetting a configuration register to indicate a Gen 5 PCIe speed.

In some embodiments, an electronic device may be configured to performone or more processes, techniques, and/or methods as described herein,or portions thereof. For example, the process may include identifying achannel type provided by a platform; identifying a presence of one ormore retimers; and choosing, based on the channel type and whether oneor more retimers are present, between 25 Gigatransfers per second (GT/s)and 32 GT/s.

In some embodiments, an electronic device may be configured to performone or more processes, techniques, and/or methods as described herein,or portions thereof. For example, the process may include identifying achannel link width from a set that includes widths of x20, x24, x28, andx28; and communicating over a channel link based on the identifiedchannel link width.

In some embodiments, an electronic device may be configured to performone or more processes, techniques, and/or methods as described herein,or portions thereof. For example, the process may include identifyingrecovered clock data from clock data recovery (CDR); and transmitting,based on the recovered clock data, transmit (TX) data after an initialtraining.

In some embodiments, a method of communicating in accordance with a PCIestandard may be provided that includes performing, by a first and secondretimer, an SKP adjustment during a first SKP ordered set (OS), andperforming, by a third and fourth retimer, an SKP adjustment during asecond SKP OS. The method can further include reducing a SKP OSfrequency by half. In some cases, the first SKP OS may be sentback-to-back with the second SKP OS. The method may further includeenhancing a training ordered set (OS) to allow for five generations ofspeeds, and setting a configuration register to indicate a Gen 5 PCIespeed. Further, a channel type provided by a platform may be identified,the presence of one or more retimers may be identified, and the channelspeed may be selected (e.g., from either 25 Gigatransfers per second(GT/s) or 32 GT/s) based on the channel type and whether one or moreretimers are present. This selection may also be determined based onwhether forward error correction (FEC) is enabled or supported. Thisspeed selection may take place during link training. These examplemethods may additional include identifying a channel link width from aset that includes widths of x20, x24, x28, and x28, and communicatingover a channel link based on the identified channel link width. Further,recovered clock data from a clock data recovery component may beidentified, and transmit data may be sent based on the recovered clockdata following training of the link.

In some embodiments, an apparatus may be provided to communicate inaccordance with a PCIe-based standard, the apparatus including anextended continuous time linear equalizer (CTLE), and/or minimum 8-tapdecision feedback equalizer (DFE), and/or a T-coil or Pi-coiltermination, and/or a data pattern filter related to clock data recovery(CDR), and/or a 4-way interleaved clock architecture, among otherexample features and components.

In some embodiments, an apparatus may be provided to communicate inaccordance with a peripheral component interconnect express (PCIe)standard with channel loss characteristics, such as discussed above. ThePCIe standard may be a Gen 5 (or higher) PCIe standard.

The following examples pertain to embodiments in accordance with thisSpecification. Example 1 is an apparatus including: an interfaceincluding a port, where the port includes a plurality ofreceiver-transmitter pairs, and each of the receiver-transmitter pairsincludes: a respective receiver to receive data on a respective one of aplurality of bidirectional lanes; and a respective transmitter totransmit data on the respective lane; and state machine logic includinghardware circuitry. The state machine logic is to: detect a trainingsequence received by a particular receiver of a particular one of theplurality of receiver-transmitter pairs on a particular one of theplurality of bidirectional lanes from a tester device, where thetraining sequence includes a value to indicate a test of the particularreceiver-transmitter pair by the tester device; cause the particularreceiver-transmitter pair to transition to a first link state inassociation with the test; and cause another one of the plurality ofreceiver-transmitter pairs to enter a second link state different fromthe first link state in association with the test.

Example 2 may include the subject matter of example 1, where the valueindicates a particular one of a plurality of test modes to be applied inthe test of the particular receiver-transmitter pair, the second linkstate corresponds to the particular test mode, and the otherreceiver-transmitter pair enters the second link state based on theparticular test mode.

Example 3 may include the subject matter of example 2, where theplurality of test modes include at least a first test mode to test lanesin presence of far-end crosstalk and at least a second test mode to testlanes in presence of near-end cross talk.

Example 4 may include the subject matter of example 3, where theparticular test mode includes the first test mode, the transmitter ofthe other receiver-transmitter pair is to remain idle in the first linkstate, the receiver of the other receiver-transmitter pair is to receivea stress signal in the first link state, the stress signal is to causecrosstalk on the particular lane, and the other receiver-transmitterpair is to ignore content of the received stress signal.

Example 5 may include the subject matter of example 3, where theparticular test mode includes the second test mode, and the transmitterof the other receiver-transmitter pair is to transmit a signal in thesecond link state to cause crosstalk on the particular lane.

Example 6 may include the subject matter of example 5, where the signalincludes a first stress signal, the second test mode is to test lanes inthe presence of both near-end and far-end cross talk, the receiver ofthe other receiver-transmitter pair is to receive a second stress signalin the second link state, the first stress signal is to cause thenear-end crosstalk on the particular lane, the second stress signal isto cause the far-end crosstalk on the particular lane, and the otherreceiver-transmitter pair is to ignore content of the received secondstress signal.

Example 7 may include the subject matter of example 3, where the secondstress signal includes a looped-back version of the first stress signal.

Example 8 may include the subject matter of any one of examples 1-7,where the first link state includes a loopback state, the tester deviceis to be the master in the loopback state.

Example 9 may include the subject matter of any one of examples 1-8,where the training sequence is received during a polling link state.

Example 10 may include the subject matter of example 9, where thepolling link state includes a link training state in a state machinecompatible with a Peripheral Component Interconnect Express (PCIe)-basedprotocol.

Example 11 may include the subject matter of example 9, where theparticular receiver-transmitter pair transitions to the first link stateand the other receiver-transmitter pair transitions to the second linkstate both from the polling link state.

Example 12 may include the subject matter of any one of examples 1-11,where the tester device includes a bit error rate tester (BERT) device.

Example 13 may include the subject matter of example 12, where the BERTdevice includes a single lane BERT device to connect to only one of theplurality of receiver-transmitter pairs during tests of the device.

Example 14 may include the subject matter of example 12, where the BERTdevice includes a multi-lane BERT device to connect to each one of theplurality of receiver-transmitter pairs during tests of the device.

Example 15 may include the subject matter of any one of examples 1-14,where the second link state includes one of a plurality of testingstates supported by the state machine logic.

Example 16 may include the subject matter of example 15, where theplurality of testing states are separate from states in a link statemachine adapted to bring a link to a standard active state.

Example 17 may include the subject matter of example 16, where thestandard active state includes an L0 state.

Example 18 may include the subject matter of any one of examples 1-17,where all of the receiver-transmitter pairs in the plurality ofreceiver-transmitter pairs other than the particularreceiver-transmitter pair are to enter the second state for the test.

Example 19 may include the subject matter of example 1, where data is tobe transmitted from the testing device on the particular lane in thefirst link state, and the second state includes one of: an idle statewhere no data is transmitted by the other receiver-transmitter pair onanother one of the plurality of lanes, a loopback state where data istransmitted continuously from the transmitter of the otherreceiver-transmitter pair on the other lane to another device during theparticular test mode and looped back to the receiver of the otherreceiver-transmitter pair; and a transmit only state where data istransmitted continuously by the transmitter of the otherreceiver-transmitter pair on the other lane and signals are ignored bythe receiver of the other receiver-transmitter pair on the other laneduring the particular test mode.

Example 20 may include the subject matter of example 19, where datatransmitted by the transmitter of the other receiver-transmitter pair isto be used to test for near-end cross-talk on the particular lane anddata transmitted from another device to the receiver of the otherreceiver-transmitter pair is to be used to test for near-end cross-talkon the particular lane.

Example 21 is a method including: receiving a training sequence at areceiver of a particular one of a plurality of receiver-transmitterpairs, where each of the plurality of receiver-transmitter pairs is toimplement a respective one of a plurality of lanes in a link, thetraining sequence is received from a tester device on a particular oneof the plurality of lanes, and the training sequence includes a value toindicate a test of the particular receiver-transmitter pair by thetester device; transitioning the particular receiver-transmitter pair toa first link state in association with the test; and transitioning oneor more other receiver-transmitter pairs in the plurality ofreceiver-transmitter pairs to enter a second link state different fromthe first link state in association with the test, where the second linkstate enables crosstalk to be produced on the particular lane during thetest.

Example 22 may include the subject matter of example 21, where the valueindicates a particular one of a plurality of test modes to be applied inthe test of the particular receiver-transmitter pair, the second linkstate corresponds to the particular test mode, and the otherreceiver-transmitter pair enters the second link state based on theparticular test mode.

Example 23 may include the subject matter of example 22, where theplurality of test modes include at least a first test mode to test lanesin presence of far-end crosstalk and at least a second test mode to testlanes in presence of near-end cross talk.

Example 24 may include the subject matter of example 23, where theparticular test mode includes the first test mode, the transmitter ofthe other receiver-transmitter pair is to remain idle in the first linkstate, the receiver of the other receiver-transmitter pair is to receivea stress signal in the first link state, the stress signal is to causecrosstalk on the particular lane, and the other receiver-transmitterpair is to ignore content of the received stress signal.

Example 25 may include the subject matter of example 23, where theparticular test mode includes the second test mode, and the transmitterof the other receiver-transmitter pair is to transmit a signal in thesecond link state to cause crosstalk on the particular lane.

Example 26 may include the subject matter of example 25, where thesignal includes a first stress signal, the second test mode is to testlanes in the presence of both near-end and far-end cross talk, thereceiver of the other receiver-transmitter pair is to receive a secondstress signal in the second link state, the first stress signal is tocause the near-end crosstalk on the particular lane, the second stresssignal is to cause the far-end crosstalk on the particular lane, and theother receiver-transmitter pair is to ignore content of the receivedsecond stress signal.

Example 27 may include the subject matter of example 23, where thesecond stress signal includes a looped-back version of the first stresssignal.

Example 28 may include the subject matter of any one of examples 21-27,where the first link state includes a loopback state, the tester deviceis to be the master in the loopback state.

Example 29 may include the subject matter of any one of examples 21-28,where the training sequence is received during a polling link state.

Example 30 may include the subject matter of example 29, where thepolling link state includes a link training state in a state machinecompatible with a Peripheral Component Interconnect Express (PCIe)-basedprotocol.

Example 31 may include the subject matter of example 29, where theparticular receiver-transmitter pair transitions to the first link stateand the other receiver-transmitter pair transitions to the second linkstate both from the polling link state.

Example 32 may include the subject matter of any one of examples 21-31,where the tester device includes a bit error rate tester (BERT) device.

Example 33 may include the subject matter of example 32, where the BERTdevice includes a single lane BERT device to connect to only one of theplurality of receiver-transmitter pairs during tests of the device.

Example 34 may include the subject matter of example 32, where the BERTdevice includes a multi-lane BERT device to connect to each one of theplurality of receiver-transmitter pairs during tests of the device.

Example 35 may include the subject matter of any one of examples 21-34,where the second link state includes one of a plurality of testingstates supported by the state machine logic.

Example 36 may include the subject matter of example 35, where theplurality of testing states are separate from states in a link statemachine adapted to bring a link to a standard active state.

Example 37 may include the subject matter of example 36, where thestandard active state includes an L0 state.

Example 38 may include the subject matter of any one of examples 21-37,where all of the receiver-transmitter pairs in the plurality ofreceiver-transmitter pairs other than the particularreceiver-transmitter pair are to enter the second state for the test.

Example 39 may include the subject matter of example 21, where data isto be transmitted from the testing device on the particular lane in thefirst link state, and the second state includes one of: an idle statewhere no data is transmitted by the other receiver-transmitter pair onanother one of the plurality of lanes; a loopback state where data istransmitted continuously from the transmitter of the otherreceiver-transmitter pair on the other lane to another device during theparticular test mode and looped back to the receiver of the otherreceiver-transmitter pair; and a transmit only state where data istransmitted continuously by the transmitter of the otherreceiver-transmitter pair on the other lane and signals are ignored bythe receiver of the other receiver-transmitter pair on the other laneduring the particular test mode.

Example 40 may include the subject matter of example 39, where datatransmitted by the transmitter of the other receiver-transmitter pair isto be used to test for near-end cross-talk on the particular lane anddata transmitted from another device to the receiver of the otherreceiver-transmitter pair is to be used to test for near-end cross-talkon the particular lane.

Example 41 is a system including means to perform the method of any oneof examples 21-40.

Example 42 may include the subject matter of example 41, where the meansinclude a computer readable-medium storing instruction executable toperform at least a portion of the method of any one of examples 21-40.

Example 43 is a system including: a device including: one or moreprocessor cores; a port including a plurality of receiver-transmitterpairs, and each of the receiver-transmitter pairs includes a respectivereceiver and transmitters and is to connect to a respective one of aplurality of bidirectional lanes; and state machine logic includinghardware circuitry. The state machine logic is to: detect a trainingsequence received by a particular receiver of a particular one of theplurality of receiver-transmitter pairs on a particular one of theplurality of bidirectional lanes from a tester device, where thetraining sequence includes a value to indicate a test of the particularreceiver-transmitter pair by the tester device; cause the particularreceiver-transmitter pair to transition to a first link state inassociation with the test; and cause another one or more otherreceiver-transmitter pairs in the plurality of receiver-transmitterpairs to enter a second link state different from the first link statein association with the test.

Example 44 may include the subject matter of example 43, furtherincluding the tester device, where the tester generates test resultsfrom the test.

Example 45 may include the subject matter of example 44, where thetester device includes a bit-error rate tester (BERT) device.

Example 46 may include the subject matter of example 45, where the BERTdevice includes a single lane BERT device to connect to only one of theplurality of receiver-transmitter pairs during tests of the device.

Example 47 may include the subject matter of example 45, where the BERTdevice includes a multi-lane BERT device to connect to each one of theplurality of receiver-transmitter pairs during tests of the device.

Example 48 may include the subject matter of example 44, where thedevice includes the tester device.

Example 49 may include the subject matter of example 43, furtherincluding a compliance fixture device to: connect to each one of theplurality of receiver-transmitter pairs using the plurality of lanes;forward data between the particular receiver-transmitter pair and thetester device; and loopback data received from transmitters of the oneor more other receiver/transmitter states in the second link state tocause both near-end and far-end crosstalk to be produced on theparticular lane during the test.

Example 50 may include the subject matter of example 43, where the valueindicates a particular one of a plurality of test modes to be applied inthe test of the particular receiver-transmitter pair, the second linkstate corresponds to the particular test mode, and the otherreceiver-transmitter pair enters the second link state based on theparticular test mode.

Example 51 may include the subject matter of example 50, where theplurality of test modes include at least a first test mode to test lanesin presence of far-end crosstalk and at least a second test mode to testlanes in presence of near-end cross talk.

Example 52 may include the subject matter of example 51, where theparticular test mode includes the first test mode, the transmitter ofthe other receiver-transmitter pair is to remain idle in the first linkstate, the receiver of the other receiver-transmitter pair is to receivea stress signal in the first link state, the stress signal is to causecrosstalk on the particular lane, and the other receiver-transmitterpair is to ignore content of the received stress signal.

Example 53 may include the subject matter of example 51, where theparticular test mode includes the second test mode, and the transmitterof the other receiver-transmitter pair is to transmit a signal in thesecond link state to cause crosstalk on the particular lane.

Example 54 may include the subject matter of example 53, where thesignal includes a first stress signal, the second test mode is to testlanes in the presence of both near-end and far-end cross talk, thereceiver of the other receiver-transmitter pair is to receive a secondstress signal in the second link state, the first stress signal is tocause the near-end crosstalk on the particular lane, the second stresssignal is to cause the far-end crosstalk on the particular lane, and theother receiver-transmitter pair is to ignore content of the receivedsecond stress signal.

Example 55 may include the subject matter of example 51, where thesecond stress signal includes a looped-back version of the first stresssignal.

Example 56 may include the subject matter of any one of examples 43-55,where the first link state includes a loopback state, the tester deviceis to be the master in the loopback state.

Example 57 may include the subject matter of any one of examples 43-56,where the training sequence is received during a polling link state.

Example 58 may include the subject matter of example 57, where thepolling link state includes a link training state in a state machinecompatible with a Peripheral Component Interconnect Express (PCIe)-basedprotocol.

Example 59 may include the subject matter of example 57, where theparticular receiver-transmitter pair transitions to the first link stateand the other receiver-transmitter pair transitions to the second linkstate both from the polling link state.

Example 60 may include the subject matter of any one of examples 43-59,where the second link state includes one of a plurality of testingstates supported by the state machine logic.

Example 61 may include the subject matter of example 60, where theplurality of testing states are separate from states in a link statemachine adapted to bring a link to a standard active state.

Example 62 may include the subject matter of example 61, where thestandard active state includes an L0 state.

Example 63 may include the subject matter of any one of examples 43-62,where all of the receiver-transmitter pairs in the plurality ofreceiver-transmitter pairs other than the particularreceiver-transmitter pair are to enter the second state for the test.

Example 64 may include the subject matter of example 63, where data isto be transmitted from the testing device on the particular lane in thefirst link state, and the second state includes one of: an idle statewhere no data is transmitted by the other receiver-transmitter pair onanother one of the plurality of lanes; a loopback state where data istransmitted continuously from the transmitter of the otherreceiver-transmitter pair on the other lane to another device during theparticular test mode and looped back to the receiver of the otherreceiver-transmitter pair; and a transmit only state where data istransmitted continuously by the transmitter of the otherreceiver-transmitter pair on the other lane and signals are ignored bythe receiver of the other receiver-transmitter pair on the other laneduring the particular test mode.

Example 65 may include the subject matter of example 64, where datatransmitted by the transmitter of the other receiver-transmitter pair isto be used to test for near-end cross-talk on the particular lane anddata transmitted from another device to the receiver of the otherreceiver-transmitter pair is to be used to test for near-end cross-talkon the particular lane.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

In the foregoing specification, a detailed description has been givenwith reference to specific exemplary embodiments. It will, however, beevident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense. Furthermore, the foregoing use of embodiment andother exemplarily language does not necessarily refer to the sameembodiment or the same example, but may refer to different and distinctembodiments, as well as potentially the same embodiment.

What is claimed is:
 1. An apparatus comprising: an interface comprisinga port, wherein the port comprises a plurality of receiver-transmitterpairs, and each receiver-transmitter pair in the plurality ofreceiver-transmitter pairs comprises: a respective receiver to receivedata on a respective one of a plurality of bidirectional lanes; and arespective transmitter to transmit data on the respective lane; andstate machine logic comprising hardware circuitry, wherein the statemachine logic is to: detect a training sequence received by a particularreceiver of a particular one of the plurality of receiver-transmitterpairs on a particular one of the plurality of bidirectional lanes from atester device, wherein the training sequence comprises a value toindicate a test of the particular receiver-transmitter pair by thetester device; cause the particular receiver-transmitter pair totransition to a first link state in association with the test; and causeanother one of the plurality of receiver-transmitter pairs to enter asecond link state different from the first link state to generatecrosstalk in association with the test.
 2. The apparatus of claim 1,wherein the value indicates a particular one of a plurality of testmodes to be applied in the test of the particular receiver-transmitterpair, the second link state corresponds to the particular test mode, andthe other receiver-transmitter pair enters the second link state basedon the particular test mode.
 3. The apparatus of claim 2, wherein theplurality of test modes comprise at least a first test mode to testlanes in presence of far-end crosstalk and at least a second test modeto test lanes in presence of near-end cross talk.
 4. The apparatus ofclaim 3, wherein the particular test mode comprises the first test mode,the transmitter of the other receiver-transmitter pair is to remain idlein the first link state, the receiver of the other receiver-transmitterpair is to receive a stress signal in the first link state, the stresssignal is to cause crosstalk on the particular lane, and the otherreceiver-transmitter pair is to ignore content of the received stresssignal.
 5. The apparatus of claim 3, wherein the particular test modecomprises the second test mode, and the transmitter of the otherreceiver-transmitter pair is to transmit a signal in the second linkstate to cause crosstalk on the particular lane.
 6. The apparatus ofclaim 5, wherein the signal comprises a first stress signal, the secondtest mode is to test lanes in the presence of both near-end and far-endcross talk, the receiver of the other receiver-transmitter pair is toreceive a second stress signal in the second link state, the firststress signal is to cause the near-end crosstalk on the particular lane,the second stress signal is to cause the far-end crosstalk on theparticular lane, and the other receiver-transmitter pair is to ignorecontent of the received second stress signal.
 7. The apparatus of claim3, wherein the second stress signal comprises a looped-back version ofthe first stress signal.
 8. The apparatus of claim 1, wherein the firstlink state comprises a loopback state, the tester device is to be themaster in the loopback state.
 9. The apparatus of claim 1, wherein thetraining sequence is received during a polling link state.
 10. Theapparatus of claim 9, wherein the polling link state comprises a linktraining state in a state machine compatible with a Peripheral ComponentInterconnect Express (PCIe)-based protocol.
 11. The apparatus of claim9, wherein the particular receiver-transmitter pair transitions to thefirst link state and the other receiver-transmitter pair transitions tothe second link state both from the polling link state.
 12. Theapparatus of claim 1, wherein the tester device comprises a bit errorrate tester (BERT) device.
 13. The apparatus of claim 1, wherein thesecond link state comprises one of a plurality of testing statessupported by the state machine logic.
 14. The apparatus of claim 13,wherein the plurality of testing states are separate from states in alink state machine adapted to bring a link to a standard active state.15. The apparatus of claim 14, wherein the standard active statecomprises an L0 state.
 16. The apparatus of claim 1, wherein all of thereceiver-transmitter pairs in the plurality of receiver-transmitterpairs other than the particular receiver-transmitter pair are to enterthe second state for the test.
 17. A method comprising: receiving atraining sequence at a receiver of a particular one of a plurality ofreceiver-transmitter pairs, wherein each of the plurality ofreceiver-transmitter pairs is to implement a respective one of aplurality of lanes in a link, the training sequence is received from atester device on a particular one of the plurality of lanes, and thetraining sequence comprises a value to indicate a test of the particularreceiver-transmitter pair by the tester device; transitioning theparticular receiver-transmitter pair to a first link state inassociation with the test; and transitioning one or more otherreceiver-transmitter pairs in the plurality of receiver-transmitterpairs to enter a second link state different from the first link statein association with the test, wherein the second link state enablescrosstalk to be produced on the particular lane during the test.
 18. Asystem comprising: a device comprising: one or more processor cores; aport comprising a plurality of receiver-transmitter pairs, wherein eachof the receiver-transmitter pairs in the plurality ofreceiver-transmitter pairs comprises a respective receiver andtransmitter and is to connect to a respective one of a plurality ofbidirectional lanes; and state machine logic comprising hardwarecircuitry, wherein the state machine logic is to: detect a trainingsequence received by a particular receiver of a particular one of theplurality of receiver-transmitter pairs on a particular one of theplurality of bidirectional lanes from a tester device, wherein thetraining sequence comprises a value to indicate a test of the particularreceiver-transmitter pair by the tester device; cause the particularreceiver-transmitter pair to transition to a first link state inassociation with the test; and cause another one or more otherreceiver-transmitter pairs in the plurality of receiver-transmitterpairs to enter a second link state different from the first link stateto generate crosstalk in association with the test.
 19. The system ofclaim 18, further comprising the tester device, wherein the testergenerates test results from the test.
 20. The system of claim 18,further comprising a compliance fixture device to: connect to each oneof the plurality of receiver-transmitter pairs using the plurality oflanes; forward data between the particular receiver-transmitter pair andthe tester device; loopback data received from transmitters of the oneor more other receiver/transmitter states in the second link state tocause both near-end and far-end crosstalk to be produced on theparticular lane during the test.